Things You'll Need
Window glass cut to size
Spring clips made for metal window frames
Single-edge razor blade
Heavy work gloves
Replacing broken windowpanes is one of the more common do-it-yourself projects of homeowners. A cracked or broken window isn't that difficult to repair, but you have to be careful when working with glass. Knowing how to refit window glass is a useful skill; it may come in handy if you own your home for many years. It takes a few basic tools to complete the task.
Remove any remaining broken pieces of glass from the window sash. Wear heavy work gloves and safety goggles, and work cautiously. Broken glass should be removed from the outside of the window whenever possible. If the glass is cracked and you can't get it out in one piece, crisscross both sides of the window glass with masking or duct tape before tapping it with a hammer, just hard enough to break the glass. The tape prevents the glass from shattering when you break it. You also may want to tape newspaper to one side of the windowpane to catch pieces of broken glass before removing the glass from the frame.
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Take out the spring clips that hold the window glass in the metal frame and put them aside. You may need to buy additional clips from a hardware store so that you have enough if any are missing.
Pry out the old glazier's putty, more commonly known as glazing compound, from the frame with a chisel or flathead screwdriver. Be careful not to damage the frame. Sand off any putty remaining on the window sash.
Measure the inside edges of the window frame for new glass. Size the glass 1/8 inch smaller than the opening in both length and width. Always recheck your measurements. Replace the windowpane with the same type of glass that was broken, making sure to use the same thickness of glass for which the window frame was manufactured. You can buy window glass at hardware or home-improvement stores. The store will cut the glass to size.
Knead a lump of window putty for a few seconds, then roll it between the palms of your hands to form a long, thin string of cord about 1/4 inch thick. The putty should feel a bit tacky. Begin at one outside corner of the window frame and go around the entire perimeter of the frame. Use a putty knife to press the glazing compound into the groove, where you will set the new pane of glass in place. Press the glass firmly into the compound to help seal out moisture.
Secure the glass in place with the spring clips, snapping them into the predrilled holes in the steel of the window frame. Clips are usually inserted at least every 6 inches around the window frame.
Seal the window around the outside edge with another long cord of putty 3/8 inch thick (about the diameter of a pencil). Press the putty into the seam between the glass and the window frame with your fingers.
Smooth the glazing compound around the pane using a putty knife. Hold the putty knife down at a 45-degree angle. Use long, even strokes, moving quickly from one side of the window frame to the other. Dip your putty knife in water between strokes to prevent the knife from sticking to the compound.
Use a razor blade to remove any excess putty from the window glass. Allow several days for the glazing compound to dry and harden.
Buy glazing compound especially designed for use with metal window sashes. Brush on linseed oil before replacing window glass to help waterproof the metal window frame and keep it from rusting. Some metal windows require the use of rubber gaskets rather than glazing compound and spring clips. If this is the case, remove the rubber gasket at the same time you remove the broken glass. Carefully pry out with the tip of a putty knife, so you can reuse the gasket if it is still in good condition. When setting in the new pane of glass, wedge the rubber gasket back in between the glass and the inside recess of the window frame. This is what holds the glass in place.